Mechanical locking device for pistons and the like



Oct. 6, 1942. R. Law 2, 97,

1 MECHANICAL LOCKING DEVICE FQR PISTONS AND THE LIKE I Filed April 30, 1941 2 Sheets- 51 1691. .1

Fly. 7. 24

0' Och-6, 1942. R. 1., LEVY 2,297,902

MECHANICAL LOCKING DEVICE FOR PISTONS AND THE LIKE I Filed April 30, 1941 2 Sheets-Sheet 2 Patented Dot. 6, 1942 MECHANICAL LOCKING DEVICE FOR PISTONS AND THE LIKE Rene Lucien Levy, Paris, France, assignor to Societe dlnventions Aeronautiques et Mccaniques S. I. A. M., Fribourg, Switzerland Application April 30, 1941, Serial No. 391,209 In France May 28, 1940 1 Claim.

Ithe mechanical locking device-which has been described in the United States Patent application No. 266,673, dated April 7, 1939, in the name of the same applicant now Pat. No. 2,221,- 9'I9in an embodiment for the unilateral locking of a piston rod, can be applied to both ends of the stroke of said rod when it is deemed desirable to ensure the locking of an under-carriage, for instance, in each of its two extreme positions.

In particular, if it is strictly compulsory to lock the under-carriage in lowered position, it is also necessary to prevent said under-carriage from becoming untimely detached in lifted position. The invention allows of obtaining this latter result in conditions which are more advantageous than the supplementary attaching devices which are often provided for that purpose on the aeroplane itself.

The present invention has as its objective a device which, whilst carrying into practice the locking principle described in the aforesaid patent application, satisfies certain peculiarities of under-carriages in which the lowering of the under-carriage is caused by thepressure of a hydropneumatic accumulator on the piston of a ack.

This pressure is permanently exerted on said piston and, normally, in devices of the type under consideration, the lowering of the under-carriage is prevented by flap-valves arranged on suitable circuits, the opening of said flap-valves being controlled by the pilot for determining the lowering of the under-carriage.

The application of the mechanical locking device to under-carriages of this kind avoids the inconveniences which might be caused by the flap-valves failing to operate.

However, considering that the pressure of the accumulator is permanently exerted on the piston of the jack, it is necessary that said pressure, efficient for lowering, should not be sufficient for causing the displacement of the slide-bolt which holds stationary the sleeve provided with claws, described in the aforesaid patent application, into locking position.

The device which will be described hereinafter.

satisfies this condition and it is characterised by he fact that the displacement of the slide-bolt, for effecting the unlocking action, is caused by the admission of air or other fluid under pressure into a special chamber of the cylinder, within which moves an auxiliary piston the rod of which is rigid with the slide.

This control of the unlocking by means of a pneumatic or hydraulic pressureindependent of that to which the main piston of the jack is subjectedcan moreover be combined with an emergency control.

The accompanying drawings illustrate an embodiment of a mechanical locking device having the above characteristic features.

In said drawings:

Fig. 1 illustrates the device in axial section, before looking.

Fig. 2 illustrates the same device in looking position.

Fig. 3 is a corresponding view at the moment the locking takes place.

In the drawings can be found the essential elements described in the aforesaid patent application, that is to say: the piston l with its rod 2, movable in the cylinder 3, the compartments 4 and 5, of variable capacity, located on either side of the piston; the admission of liquid under pressure 6, which, in the application under consideration, is connected to the hydropneumatic accumulator; the sleeve provided with claws l, 8, 9; the slide-block forming the bolt H); the restoring spring [3 for said slide-block; the sleeve I5 the inner wall of which forms a track for pinching the claws 8, 9; the disengaging incline H5 at the end of said track.

According to the present invention, the slidebolt I0 is rigid, through the medium of a rod IT, with an auxiliary unlocking piston l8 which can move within a chamber [9 provided in the main cylinder I, at the rear of a fixed bottom 20 of said cylinder.

The rod ll passes through said bottom 20 and fluid-tight packings 2| are provided for avoiding any communication of fluid between the compart ments 5 and I9.

Likewise, fluid-tight packings 22, 23 are provided at, the contact surface of the cylinder with the auxiliary piston l8 and the bottom 20.

In the compartment 19 opens a conduit 24 for air under pressure.

The locking action takes place in conditions similar to those which have been described in the aforesaid patent application, the pinched claws 9 encountering the slide 10 and pushing the latter back in the direction of the arrow ,f, until said claws coming at right angles to the disengaging incline l6, resiliently spread out, the spring l3 then pushing back the slide in the direction reverse to the arrow and consequently ensuring the locking.

For causing the unlocking action, it suffices, normally, to send air under pressureor other fluid under pressurein the conduit 24.

This admission of air for unlocking the jack can constitute a preliminary operation efiected by the pilot before he acts on the flap-valves the opening of which allows the displacement of the main piston I in the direction for lowering the under-carriage.

The air under pressure admitted into the compartment [9 acts on the portion S of the auxiliary piston l8 and causes the displacement of the slide-bolt IQ in the direction of the arrow 1, thus releasing the claws 8, 9.

The hydraulic pressure which is permanently exerted in the compartment 5 connected, at 6, to the hydropneumatic accumulator (not shown) determines the displacement of the main piston in the direction reverse to the arrow f, the claws 9 then sliding on the disengaging incline It.

The unlocking being thus effected, the displacement of the main piston continues up 'to the end of the lowering stroke.

In case of accident, breakingor the like, of the'conduit 2A, the unlocking can be determined by sending into the compartment 5, through the conduit 6 or through any other suitable connection, a liquid under sumcient pressure for c'o'mpelling, the pressure being exerted on the portion S, the slide It to withdraw in the direction J.

In the example considered, the main piston is provided with two sleeves provided with claws,

"one, I, 8, 9, the operation of which has just been set forth, the other 7a, 8a, 9a, carried by the opposite face of the main piston I and cooperating with a slide-bolt mounted at the opposite end of the cylinder.

What I claim as my invention and desire to secure by Letters Patent is:

A mechanical locking device for pistons comprising in combination, a cylinder, a piston in the cylinder, a resilient sleeve rigidly connected to the piston, claws on the sleeve, means having a guide surface and a disengaging incline rigidly connected to th cylinder, said sleeve and claws slidable within the guide means with the guide surface contracting the claws, a slide, resilient means urging the slide in one direction, and capable of being encountered and pushed back by said sleeve in contracted condition, of first moving back in front of said sleeve until the edge of the claws of the latter reaches the fixed disengaging incline, forming an extension of the guide surface and allowing the sleeve to again resiliently spread out so that the slide under the action of the resilient force which urges it, progresses within the sleeve and applies said claws against the disengaging incline, the backward 'movement of the piston being thus prevented, means fcrminga chamber separate from the cylinder chamber in which the piston is located, an auxiliary piston connected to the slide ar movable within the separate chamber of cylinder, means for introducing a fluid under pressure into said separate chamber so as to cause the displacement of the slide in the direction fer releasing said sleeve, whereby the piston 'to be locked is displaced.

RENE LUCIEN LEVY, 

